In the quest for greater efficiency, there is a move to using higher voltage for power distribution in data-centers and like installations. Presently, data-centers usually distribute power as 3-phase 208 V ac or possibly 3-phase 240 V ac, the latter being more common abroad. Telecom centers usually distribute power as 48 V dc. 48 V dc is safe both for shock hazard and arc-flash. The voltage necessary to sustain an arc is in the order of 60 V dc. 208 V ac is generally considered not susceptible to arc-flash if sourced from a transformer of 125 kVA or less. 208 V ac is high enough to be a shock hazard, and ground fault (gfi) breakers are often used to reduce the risk. At higher currents, gfi breakers are not available.
Now, 380 V dc, as split plus and minus 190 Vdc is being considered for power distribution, as is 480 V ac 3-phase, as examples, not limitations. Both voltages are well above the threshold at which arc-flash becomes an issue, and both are high enough to present a serious shock hazard.
It is well known to use insulation to reduce the risk of shock, but many parts of a power distribution circuit customarily are not insulated, particularly the bus bars in distribution panels and switch gear. It is known but not widely practiced to use insulated bus bars to reduce the risk of arc-flash.
Arc-flash may be initiated by an inadvertent short circuit, but another common cause is a deteriorating connection. As the resistance of the connection increases, heat is generated, which can result in a degenerating situation resulting in failure of the connection. This may be accompanied by high heat and arcing, which can then arc to ground or another conductor as an arc-flash incident.